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Alton, Illinois

City in Madison County, Illinois

Air quality

The air at Alton

Index 14, good, led by fine particles. Read at 7 PM from its reporting area, St. Louis (Metro-east) (IL), 24 miles off.

14Good
  • Fine particles (PM2.5)14Good3.6 mi
  • Ozone13Good14 ppb3.6 mi
  • Coarse particles (PM10)3Good13.5 mi
  • Nitrogen dioxide2Good2.7 ppb4.5 mi
  • Sulfur dioxide0Good0.4 ppb17 mi
  • Carbon monoxide-0.1 ppm17 mi

The days ahead

Good each day through Mon Oct 19, led by fine particles. Yesterday measured 39, good.

Smoke, the next 42 hours

No smoke near the ground through Sun 1 PM.

FriSatSun

Precipitation

What has fallen at Alton

0.13 in in the last 24 hours, 0.95 in over the last 3 days, to Fri 7 PM. Measured by radar and rain gauges, as water.

Last 24 hours
0.13in
Last 3 days
0.95in

Visibility

How far you can see at Alton, the next 42 hours

Visibility stays 9 miles or more through Sun 1 PM, lowest 10 miles Sat 6 AM.

FriSatSun

On the radar over Alton, IllinoisReflectivityStorm topsRain rateRain, last 24 hoursForecast temperatureForecast rain totalEvery picture

What is measuring near here

The 6 instruments nearest Alton, how far away each one is, how high it stands, and what kind of measurement it makes. The nearest is 1.5 miles away.

measured now4 instruments

measured daily2 instruments

AltonALNI2

At a cooperative observer's station/2.0 mi away/394 ft/114 ft below here

snowfall, snow depth, precip, high, low

Rank784of 1,419

Wood River 0.5 NWIL-MD-24

In a volunteer observer's own ground/4.2 mi away/440 ft/68 ft below here

precip, snowfall, snow depth

Rank-

Station report

The weather at Alton/St Louis R, drawn

The nearest airport reporting now, 5.9 mi from Alton, Illinois. From its report of Oct 16, 2026, 7:45 PM local time: 3 of its 6 sheets.

The sky

Broken at 6,500 ft, overcast at 8,000 ft; the ceiling is 6,500 ft; visibility 10 mi or more.

Section of the sky over Alton/St Louis R, height above the station to scale: broken cloud with its base at 6,500 feet, overcast cloud with its base at 8,000 feet, the ceiling at 6,500 feet, and visibility of 10 mi or more.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT ALNFIG. A THE SKY OVER ALTON/ST LOUIS RSECTION, HEIGHT ABOVE THE STATION TO SCALE, EACH LAYER AT THE HEIGHT OF ITS BASE AS REPORTED; COVER IN EIGHTHS OF THE SKY; TOPS NOT MEASUREDFT ABOVE THE STATION02,5005,0007,50010,00012,500ETAGESLOWMIDDLETHE STATIONOVC 8,000 FTOVERCAST, 8 EIGHTHS OF THE SKYBKN 6,500 FTBROKEN, 5 TO 7 EIGHTHS OF THE SKYCEILING 6,500 FTVISIBILITY, MILES: 10 MI OR MORE0510TITLEAlton/St Louis R, the skySTATION REPORT · ASOS ALNTYPESECTIONSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 1 of 6DATE2026-10-17IDSR-ALN-1DRAWN AS linework on paperSOURCES FB-SKY-001, FB-SKY-013, FB-SKY-014

The air

51.8 F with a dew point of 48.2 F, 87 per cent relative humidity. Air lifted from the station would cool to its dew point, where cloud forms, about 800 ft up; the lowest cloud reported is at 6,500 ft.

Chart of the air at Alton/St Louis R: temperature 51.8 degrees Fahrenheit and dew point 48.2, 87 per cent relative humidity; air lifted from the station cools along the dry rate and meets its dew point about 800 feet above the station, against the lowest cloud reported at 6,500 feet; height to scale.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT ALNFIG. B THE AIR AT ALTON/ST LOUIS RTHE REPORTED TEMPERATURE AND DEW POINT, AND AIR LIFTED FROM THE STATION WITHOUT MIXING UNTIL IT SATURATES; HEIGHT ABOVE THE STATION TO SCALEFT ABOVE THE STATION01,0002,0003,0004,0005,00040 F50 F60 FSATURATES 800 FT ABOVE THE STATION, AT 47.3 FABOVE THIS SHEET: LOWEST CLOUD REPORTED, BKN 6,500 FTTEMPERATURE 51.8 FDEW POINT 48.2 FSPREAD 3.6 FRELATIVE HUMIDITY 87 PER CENTTHE AIR COOLS ABOUT 5.4 F EACH 1,000 FT IT RISES, AND ITS DEW POINT ABOUT 1 FSOLID: THE LIFTED AIR'S TEMPERATURE; DASHED: ITS DEW POINTTITLEAlton/St Louis R, the airSTATION REPORT · ASOS ALNTYPECHARTSCALEHEIGHT TO SCALEREVAS REPORTED SHEET 2 of 6DATE2026-10-17IDSR-ALN-2DRAWN AS linework on paperSOURCES FB-WAT-020, FB-WAT-002, FB-ENG-011, FB-ENG-005

The wind

From the north northwest (330 degrees) at 12 mph: force 3, a gentle breeze on the Beaufort scale. The strongest gust today was 33 mph.

Plan of the wind at Alton/St Louis R, north up: blowing from 330 degrees, the north northwest, at 12 miles an hour; beside it the Beaufort scale from calm to hurricane force, force 3, gentle breeze, marked.1122334455667788AABBCCDDEE© 2026 STORM STATION 247THE FIELD BOOKSTATION REPORT ALNFIG. C THE WIND AT ALTON/ST LOUIS RPLAN, NORTH UP: THE WIND AS REPORTED, AND WHERE IT SITS ON THE BEAUFORT SCALENESWTHE STATIONFROM 330°BEAUFORT FORCELEAST WIND, MPH0CALM01LIGHT AIR12LIGHT BREEZE43GENTLE BREEZE8NOW, 12 MPH4MODERATE BREEZE135FRESH BREEZE196STRONG BREEZE257NEAR GALE328GALE399STRONG GALE4710STORM5511VIOLENT STORM6412HURRICANE FORCE73TITLEAlton/St Louis R, the windSTATION REPORT · ASOS ALNTYPEPLAN north upSCALENOT TO SCALEREVAS REPORTED SHEET 3 of 6DATE2026-10-17IDSR-ALN-3DRAWN AS linework on paperSOURCES FB-EVT-150, FB-ENG-008, FB-INS-002

The full report of Alton/St Louis R, in 6 sheets, each beside the Field Book plates that explain it

0in

Snow on the ground

Measured at Alton (ALNI2), 2.0 miles from here, read 16 Oct, 05:00. measured daily

Elsewhere in Illinois

23 places, each with its own forecast and its own instruments.

Near Alton

The nearest places, each with its own forecast and the instruments nearest it.

Near Alton

River and lake gauges